This Letter presents a new design of balanced-to-unbalanced (B2U) filtering magic-T based on circular patch resonator. Without additional circuit, the prescribed in-phase and out-of-phase specifications of the magic-T are achieved by elaborately studying and exploring the electric field distributions of the degenerate resonant modes in the circular patch resonators. Meanwhile, the desired filtering responses are attained by virtue of the coupling extent between the two designed patch resonators in the back-to-back form. In the proposed design, a pair of TM 11 modes at first make up passband. Meanwhile, nice common-mode suppression can be achieved at the balanced ports, and high isolation is achieved at the single-end ports, respectively. For demonstration, a prototype B2U filtering magic-T working at 4.3 GHz with 3 dB fractional bandwidth of 16.3% is implemented. Measured results coincide well with simulated ones, verifying the proposed design concept.

中文翻译：

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基于高选择性圆形贴片谐振器的平衡到不平衡滤波magic-T

本文介绍了一种基于圆形贴片谐振器的平衡到不平衡 (B2U) 滤波magic-T 的新设计。无需额外电路，通过精心研究和探索圆形贴片谐振器中简并谐振模式的电场分布，实现magic-T的规定同相和异相规格。同时，通过背对背形式的两个设计的贴片谐振器之间的耦合程度，获得了所需的滤波响应。在建议的设计中，首先由一对 TM 11 模式组成通带。同时，平衡端口可实现良好的共模抑制，单端端口分别实现高隔离度。为了演示，原型 B2U 滤波 magic-T 在 4.3 GHz 下工作，3 dB 分数带宽为 16。3% 被执行。实测结果与模拟结果吻合良好，验证了所提出的设计理念。